Date: Wed, 14 Apr 2010 22:22:56 +0200 From: =?ISO-8859-1?Q?Fernando_Apestegu=EDa?= <fernando.apesteguia@gmail.com> To: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Understanding proc_rwmem Message-ID: <x2l1bd550a01004141322m420065fbj742800c3e4a81927@mail.gmail.com>
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Hi all,
I'm trying to read process memory other than the current process in
kernel. I was told to use the proc_rwmem function, however I can't get
it working properly. At first, I'm trying to read how many elements
the environment variables vector has. To do this I tried this from a
linprocfs filler function:
struct iovec iov;
struct uio tmp_uio;
struct ps_strings *pss;
int ret_code;
buff = malloc(sizeof(struct ps_strings), M_TEMP, M_WAITOK);
memset(buff, 0, sizeof(struct ps_strings));
PROC_LOCK_ASSERT(td->td_proc, MA_NOTOWNED);
iov.iov_base = (caddr_t) buff;
iov.iov_len = sizeof(struct ps_strings);
tmp_uio.uio_iov = &iov;
tmp_uio.uio_iovcnt = 1;
tmp_uio.uio_offset = (off_t)(p->p_sysent->sv_psstrings);
tmp_uio.uio_resid = sizeof(struct ps_strings);
tmp_uio.uio_segflg = UIO_USERSPACE;
tmp_uio.uio_rw = UIO_READ;
tmp_uio.uio_td = td;
ret_code = proc_rwmem(td->td_proc, &tmp_uio);
if (ret_code == 0) {
sbuf_printf(sb, "proc_rwmem successfully executed: %d\n", ret_code);
} else {
sbuf_printf(sb, "Error in proc_rwmem: %d\n", ret_code);
}
pss = (struct ps_strings *)(iov.iov_base);
sbuf_printf(sb, "ps_nargvstr = %d\nps_nenvstr = %d\n",
pss->ps_nargvstr, pss->ps_nenvstr);
free(buff, M_TEMP);
Considering I left security and error handling aside, what is wrong
with the code above?
proc_rwmem returns 0 indicating no failure, but when I try to print
the result, I get random stuff. I thought maybe the problem is in the
uio_offset field, but p->p_sysent->sv_psstrings is a vm_offset_t. Is
the offset properly specified? If not, what else could be the problem?
Thanks in advance.
PS: I posted a similar question at forums.freebsd.org but got no
answer, that is why I ask here.
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